1. Field of the Invention
The present invention relates to a fuel injection valve used mainly in a fuel supply system for an internal combustion engine, and particularly to an improvement in a fuel injection valve comprising: a valve member; a valve seat member which has a valve seat cooperating with said valve member, and a valve seat bore leading to a downstream end of said valve seat and opening at a front end face said valve seat member; an injector plate coupled to the front end face of said valve seat member and having a plurality of fuel injection orifices; and a flat fuel diffusion chamber provided between said valve seat member and said injector plate to widen radially outwards from an outer end edge of said valve seat bore for dispensing a fuel received therein from said valve seat bore to the plurality of fuel injection orifices in a diffusing manner.
2. Description of the Related Art
A conventional fuel injection valve is already known, as disclosed in, for example, Japanese Patent Application Laid-open No. 2000-97129.
The conventional injection valve has the following advantage: During opening of the valve member, a high-pressure fuel passed through the valve seat is allowed to flow at a high speed into the fuel diffusion chamber to be diffused, thereby promoting the atomization of the fuel injected from each of the fuel injection orifices in the injector plate and forming stable fuel spray forms.
Accordingly, it is an object of the present invention to provide a fuel injection valve, wherein the fuel-diffusing function of the fuel diffusion chamber can be further enhanced, to thereby further promote the atomization of the fuel injected from the fuel injection orifices and to form more stable fuel spray forms.
To achieve the above object, according to a first feature of the present invention, there is provided a fuel injection valve comprising: a valve member; a valve seat member which has a valve seat cooperating with said valve member, and a valve seat bore leading to a downstream end of said valve seat and opening at a front end face said valve seat member; an injector plate coupled to the front end face of said valve seat member and having a plurality of fuel injection orifices; and a flat fuel diffusion chamber provided between said valve seat member and said injector plate to widen radially outwards from an outer end edge of said valve seat bore for dispensing a fuel received therein from said valve seat bore to the plurality of fuel injection orifices in a diffusing manner; wherein an annular step is formed on a ceiling surface of said fuel diffusion chamber so that a level of the ceiling surface is gradually lowered radially outwards, and said fuel injection orifices are disposed immediately below said step and at a distance from an inner peripheral wall of said fuel diffusion chamber.
With the first feature, during opening of the valve member, the fuel transferred from the valve seat bore into the flat fuel diffusion chamber flows to spread radially. Thereafter, the fuel flowing along the ceiling surface of the fuel diffusion chamber collides with the annular step to be scattered to the periphery, and the flow flowing along a bottom surface of the fuel diffusion chamber collides with the inner peripheral wall of the chamber to be scattered while being bounced back therefrom. The scattered fuel portions again collide with one another immediately above the plurality of fuel injection orifices, whereby the fierce turbulent flow and diffusion of the fuel are caused. As a result, the atomization of the fuel injected from the fuel injection orifices can be effectively promoted, and stable fuel spray forms can be formed and drawn into the engine along with intake air, while being prevented from being deposited to an inner wall of an intake passage for the engine to the utmost. Thus, it is possible to provide enhancements in startability and output performance of the engine as well as a reduction in fuel consumption.
According to a second feature of the present invention, in addition to the first feature, a diameter of a pitch circle of the plurality of fuel injection orifices is equal to a diameter of the annular step.
With the second feature, the fuel turbulent flow generated in the fuel diffusion chamber can be injected with a good efficiently from the fuel injection orifices, thereby effectively promoting the atomization of the fuel.
According to a third feature of the present invention, in addition to the first or second feature, the valve seat bore is formed into a funnel-shape having a diameter increasing toward the fuel diffusion chamber.
With the third feature, the flowing of the fuel from the valve seat bore into the fuel diffusion chamber can be smoothened, whereby a high speed of collision of the fuel with the annular step can be maintained, and the atomization of the fuel injected from the fuel injection orifices can be promoted.
According to a fourth feature of the present invention, in addition to the first or second feature, a plurality of the annular steps having different diameters are formed in a stair-shape on the ceiling surface of the fuel diffusion chamber, and a plurality of the fuel injection orifices are disposed on each of a plurality of pitch circles having different diameters in correspondence to the annular steps, respectively.
With the fourth feature, the fuel transferred from the valve seat bore into the fuel diffusion chamber collides sequentially with the stair-shaped annular steps and the inner peripheral wall of the fuel diffusion chamber, whereby more fierce turbulent flow and diffusion of the fuel are caused, so that the atomization of the fuel injected from the fuel injection orifices can be further effectively promoted.
The above and other objects, features and advantages of the invention will become apparent from the following description of the preferred embodiments taken in conjunction with the accompanying drawings.